how do i save the data in micro controller(I am using stm32f7276zi nucleio 144) so that even after i reset i could use that data
If you erase/save a lot of data then use external flash part, SPI or QSPI, or I2C flash memory.
You might save to program flash, but wear leveling will be very important.
Here is an example of an stm32f103 using internal flash. As previous post says:wear levelling is important.